What makes a galaxy radio-loud?

TL;DR

This study compares the spectral energy distributions of different AGN types, revealing that radio-loudness correlates with black hole and bulge mass, and suggesting two main AGN categories distinguished by these properties.

Contribution

It demonstrates that radio-loud and radio-quiet AGNs differ primarily in black hole and bulge mass, based on SED analysis of SDSS samples.

Findings

RLAGNs have SEDs similar to quasars.

Black hole masses increase from IG-AGNs to RLAGNs.

All AGNs accrete near 10% of the Eddington limit.

Abstract

We compare the Spectral Energy Distribution (SED) of radio-loud and radio-quiet AGNs in three different samples observed with SDSS: radio-loud AGNs (RLAGNs), Low Luminosity AGNs (LLAGNs) and AGNs in isolated galaxies (IG-AGNs). All these galaxies have similar optical spectral characteristics. The median SED of the RLAGNs is consistent with the characteristic SED of quasars, while that of the LLAGNs and IG-AGNs are consistent with the SED of LINERs, with a lower luminosity in the IG-AGNs than in the LLAGNs. We infer the masses of the black holes (BHs) from the bulge masses. These increase from the IG-AGNs to the LLAGNs and are highest for the RLAGNs. All these AGNs show accretion rates near or slightly below 10% of the Eddington limit, the differences in luminosity being solely due to different BH masses. Our results suggests there are two types of AGNs, radio quiet and radio loud, differing only by the mass of their bulges or BHs.